Mixed adsorption and surface tension prediction of nonideal ternary surfactant systems

To deal with the mixed adsorption of nonideal ternary surfactant systems, the regular solution approximation for nonideal binary surfactant systems is extended and a pseudo-binary system treatment is also proposed. With both treatments, the compositions of the mixed monolayer and the solution concentrations required to produce given surface tensions can be predicted based only on the gamma-LogC curves of individual surfactants and the pair interaction parameters. Conversely, the surface tensions of solutions with different bulk compositions can be predicted by the surface tension equations for mixed surfactant systems. Two ternary systems: SDS/Hyamine 1622/AEO7, composed of homogeneous surfactants, and AES/DPCl/AEO9, composed of commercial surfactants, in the presence of excess NaCl, are examined for the applicability of the two treatments. The results show that, in general, the pseudo-binary system treatment gives better prediction than the extended regular solution approximation, and the applicability of the latter to typical anionic/cationic/nonionic nonideal ternary surfactant systems seems to depend on the combined interaction parameter, $${\mathop {(\beta }\nolimits_{an}^s } + {\mathop \beta \nolimits_{cn}^s })/2 - {\mathop \beta \nolimits_{ac}^s }/4$$ : the more it deviates from zero, the larger the prediction difference. If $${\mathop {(\beta }\nolimits_{an}^s } + {\mathop \beta \nolimits_{cn}^s })/2 - {\mathop \beta \nolimits_{ac}^s }/4$$ rarr0, good agreements between predicted and experimental results can be obtained and both treatments, though differently derived, are interrelated and tend to be equivalent

Removal of Tannic Acid From Aqueous Solution by Cloud Point Extraction and Investigation of Surfactant Regeneration by Microemulsion Extraction

The aim of this work is the extraction of tannic acid (TA) with two commercial nonionic surfactants, separately: Lutensol ON 30 and Triton X-114 (TX-114).The experimental cloud point extraction results are expressed by four responses to surfactant concentration and temperature variations: extent of TA extraction (E), remaining solute (X s,w) and surfactant (X t,w) concentrations in dilute phase and volume fraction of coacervate (Φc) at equilibrium. An empirical smoothing method was used and the results are represented on three dimensional plots. In optimal conditions, the extraction extent of TA reaches 95 and 87 % using TX-114 and Lutensol ON 30, respectively. Sodium sulfate, cetyltrimethylammonium bromide (CTAB) addition and pH effect are also studied. Finally, the possibility of recycling of the surfactant is proved

The politics of suspects’ geo-genetic origin in France: The conditions, expression, and effects of problematisation

International audienceRecently, genetics has given rise to changes in how people’s origin is conceived. Forensics has started using some of these changes in the shape of new DNA-based tests aimed at determining suspects’ geographic origin. This article analyses how recent practices in this field have been ‘problematised’ in France, in Foucault’s sense of the term, and gives substantial weight to the country’s historical and republican legacy. First, the launch of these genetic tests is examined, looking at the work of actors who helped create the preconditions for this problematisation but at the same time tried to deconstruct it. The paper goes on to focus on how this problematisation is expressed, questioning the arguments used particularly by its opponents who ground their stance in history, law, and science, while also invoking ethical and political concerns regarding data use. Finally, current state regulations on the matter are outlined, showing how ‘points of problematisation’ have been construed in terms of prohibition. The article concludes by underlining the internal tensions (the ‘knot’) of the problematisation process, showing how it highlights changes in contemporary notions of origin and the types of subjects it produces. More generally, the implications of this study for social science research on origin and on the life sciences are also discussed